Five Chinese big-headed turtles — which will only grow to about seven inches long — were born in November in the Prospect Park Zoo, an extremely rare occurrence, the Wildlife Conservation Society said Monday.

The endangered species has a skull of solid bone — which means it can’t be pulled into the turtle’s shell, the WCS said.

The turtles were bred in an effort to save the species from extinction, officials said. There are now 15 of the creatures between the Bronx and Prospect Park Zoos, the largest collection of any other facility accredited by the Association of Zoos and Aquariums, officials said.

“With so many of the world’s freshwater turtles and tortoises facing extinction, these hatchlings represent significant progress for the conservation of the species,” said Denise McClean, director of the Prospect Park Zoo.

The turtles are native to China, Cambodia, Laos, Myanmar, Thailand and Vietnam, zoo officials said. Most are kept out of public view — including the new hatchlings — but one adult female is on exhibit at the Prospect Park Zoo.

Julie Larsen Maher / Wildlife Conservation Society

One of five Chinese big-headed turtles that hatched at the Prospect Park Zoo.